Before exiting Arbil make sure that you have saved all your changes. This can easily be done by the key short-cut CTRL/CMD+S.

You can exit Arbil by closing the main window, or through File -> Exit on Windows or Linux, or Arbil -> Quit Arbil on Mac OS. In case of unsaved changes a message will appear and ask if you wish to Save Changes Before Exiting; choose Yes or No, Arbil is now closed.